Pipes and conduits have been restored for many years using a variety of rehabilitation and pipelining techniques. One such technique is referred to as “cured-in-place pipelining” or “CIPP.” This technique includes taking a resin-absorbent sheet, impregnating the sheet with resin, placing the resin-impregnated sheet against the wall of a pipe, and allowing the resin to cure and harden. The resin-absorbent sheets are generally known as “liners.”
Some liners used for cured-in-place pipelining applications use a layer of resin-absorbent fabric in association with a coating, reinforcing, and/or shielding layer. For example, U.S. Pat. No. 4,009,063 to Wood is one of the first patents issued for such liners. The '063 patent discloses a two-layered liner comprising a laminate of non-woven felt and plastics sheet material. The '063 patent also suggests the use of a second sheet of material in the form of a woven scrim web to reinforce the liner. The patent fails to disclose where the scrim web is incorporated into the liner. Furthermore, the '063 patent discloses a laminate for use with a so-called “pull-in-and-inflate” method that does not utilize an inversion process for installation. Inventor Eric Wood was also issued U.S. Pat. No. 4,836,715, which discloses a similar liner where a woven layer may be used as a reinforcing layer within sections of a felt layer. As such, this patent does not specifically disclose the placement of a scrim layer on the surface of the liner.
Another example of such liners are disclosed in U.S. Pat. No. 5,501,248 and U.S. Patent Application Number 2010/0243091, where the use of a polymeric coating reinforced with a scrim associated with a resin-absorbent fabric layer is described. Since the polymeric coating and scrim are attached or otherwise abut, these liners are subject to delamination of the polymeric coating from the liner after placement within a host pipe.
U.S. Pat. No. 5,535,786 to Mäkelä, et al discloses a pipe liner of various constructions where one or more felt layers are used in conjunction with a knitted reinforcement layer and an optional coating. Even though the several embodiments of this patent disclose a variety of configurations of the felt layer, reinforcement layer, and coating layer, there is no embodiment where the reinforcement layer is connected to one surface of a single layer of felt with a coating on the opposite surface.
U.S. Pat. No. 5,868,169 to Catallo discloses the use of a layer of reinforcing fibers and a layer of resin-absorbing material fixedly attached and positioned adjacent to the layer of reinforcing fibers so that the layers of resin-absorbing material, when saturated with resin, shield the layer of reinforcing fibers from water or other corrosive materials that contact the liner. The patent teaches that with conventional cured-in-place liners using fiberglass, the fiberglass fibers located on the inner and outer surfaces of the liner are exposed to the water and other corrosive materials. Due to capillary or wicking action, the water and other corrosive materials are absorbed into the tiny spaces adjacent to the exposed fiberglass fibers. The absorption of water and other corrosive materials enhances the expansion and contraction of the resin and fiberglass, thereby further deteriorating the bond between the resin and fiberglass. Corrosive reactions with the resin/fiberglass laminant also exacerbate the deterioration of the bond between the resin and fiberglass. Because of the wicking action, the space between the resin and fiberglass fibers becomes progressively larger and larger. In addition, as the space between the resin and a given fiber grows in size and length, previously unexposed fiberglass fibers adjacent to the exposed fibers become exposed to the water and other corrosive materials. Over time, the wicking of water and other corrosive materials into the laminant will destroy the bond between the resin and the fiberglass fibers. When this occurs, the reinforcing effects of the fiberglass is lost causing the liner to lose much of its structural strength, thereby ending the useful life of the liner prematurely. As with the Wood patents, the Catallo patent fails to teach the inversion of such a liner into a pipe during installation.
U.S. Pat. No. 6,732,763 to Williamson, et al. addresses many of the same problems as the '169 patent, but claims to additionally prevent stretch. U.S. Pat. No. 6,732,763 discloses a stretch-resistant liner for a pipe having a support sleeve positioned between two sealing sleeves. As the support layer is sandwiched between two sealing layers, the flexural strength of the cured liner is not enhanced because the reinforcement is placed close to the neutral plane of the liner.
Yet another liner used in cured-in-place pipelining having a layer of resin-absorbent fabric in association with a coating, reinforcing, and/or shielding layer is disclosed in U.S. Pat. No. 6,708,729 to Smith. This patent discloses a multi-layered liner construction where a scrim web is attached to a layer of resin-absorbent material to act as a reinforcing layer. An inner reinforcing layer comprising bundles of reinforcing fibers may be attached to the scrim web, folded over, and stitched along the edge to form a tube. A resin-absorbent layer or layers are wrapped about the inner reinforcing tubular layer and joined at the edges to form a tube. An outer reinforcing layer of reinforcing fiber bundles held together by longitudinal stitching is then wrapped around the resin-absorbent layer to form an outer tubular layer with the ends of the bundles of reinforcing fibers overlapping. The result is multi-layered liner with a scrim web near one surface of the liner and an impermeable coating near the opposite surface of the liner.
As such, problems remain in the art and a need exists for an improved method and means for repairing a pipe using a scrim-reinforced pipe liner.